There are numerous devices with a photographing function, e.g., a camera, a video recorder, a mobile terminal with a photographing function (e.g., a handset, a notebook computer, a tablet computer, a POS machine, an in-vehicle computer, etc.), etc. These devices with a photographing function generally function as follows: when a photographing mode is enabled by a user, imaging optical sensors in these devices can capture a picture to be taken and display it to the user for preview, that is, when the photographing mode is enabled by the user, the devices with the photographing function can acquire a preview image of the picture to be taken and display the preview image to the user for preview to thereby make it convenient for the user to select an appropriate angle according to the preview image so as to take the picture.